Process for extruding polypropylene

ABSTRACT

A process for extruding polypropylene comprising extruding a composition comprising a polypropylene and a second acid scavenger and less than about 10 ppm of a nucleating agent.

TECHNICAL FIELD OF THE INVENTION

The present invention is directed to the process of extrudingpolypropylene compositions with acid scavengers and low levels ofnucleating agents.

BACKGROUND

There are some non-nucleated polypropylene (PP) grades, for examplebiaxially oriented polyproplylene (BOPP), where a consistent base-linecrystallization temperature is required. In BOPP, changes incrystallization rates may affect several processing variables—the pointin the process where the film is quenched (or freezes), the temperatureat which the film is successfully oriented, and the amount oforientation that can be achieved under standard processing conditions.If a BOPP film becomes inadvertently nucleated, it is well known in theindustry that processing problems may be encountered—chief among theseis for the film to tear or split in the machine direction as it is beingoriented transversally.

Likewise if an injection molding polypropylene grade becomesinadvertently nucleated, it is possible that the shrinkagecharacteristics may be altered. Therefore, an injection molded articlehaving demanding dimensional tolerances may shrink too much and fall outof specification if made with the inadvertently nucleated composition.

Similar processing problems and/or physical property problems may existwith a wide variety of part fabrications when the incoming polypropylenebecomes inadvertently nucleated if the part fabrication was initiallyestablished with non-nucleated polypropylene.

A need therefore exists for additives and processes that can reduce oreliminate any residual nucleation in non-nucleated polypropylene grades.

BRIEF SUMMARY OF THE INVENTION

A process for extruding polypropylene containing extruding a firstcomposition forming a first extrudate then a second composition forminga second extrudate. The first composition contains a firstpolypropylene, a nucleating agent, and a first acid scavenger, where thenucleating agent is in an amount of at least about 50 ppm. The secondcomposition contains a second polypropylene and a second acid scavengerand where the second extrudate contains less than about 10 ppm of anucleating agent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a graph showing the T_(c) of the formulation ofExamples 5, 6, and 7 versus time.

DETAILED DESCRIPTION

The following definitions are provided to define several of the termsused throughout this application.

When the term “stearate” is used in the application, the term is used toinclude mono, di, and tri stearates depending on the metal cation andits valency. Additionally, when a compound is designated a “stearate”,the compound may also contain low amounts of other fatty acids such aspalmitate, myristate, etc which are characteristic of commercial gradesof stearates. The term “fatty acids” may also include chemicalderivatives such as (but not limited to) 12-hydroxy stearates,lactylates, and lactate esters.

As used herein, the term “acid neutralizer” or “acid scavenger” refersto those classes of additives which may be used to neutralize acidicspecies related to or created by residual amounts of catalyst used inthe polymerization reaction in polypropylene manufacturing. Theseneutralizers or scavengers may also serve other purposes as well in theformulation such as color improvement, lubricity, or as a mold releaseagent.

Unless otherwise indicated, conditions are 25° C., 1 atmosphere ofpressure and 50% relative humidity, concentrations are by weight, andmolecular weight is based on weight average molecular weight. The term“polymer” as used in the present application denotes a material having aweight average molecular weight (M_(w)) of at least 5,000. The term“copolymer” is used in its broad sense to include polymers containingtwo or more different monomer units, such as terpolymers, and unlessotherwise indicated, includes random, block, and impact copolymers. Theconcentration of ethylene or propylene in a particular phase or in theheterophasic composition is based on the weight of reacted ethyleneunits or propylene units relative to the total weight of polyolefinpolymer in the phase or heterophasic composition, respectively,excluding any fillers or other non-polyolefin additives. Theconcentration of each phase in the overall heterogeneous polymercomposition is based on the total weight of polyolefin polymers in theheterophasic composition, excluding any fillers or other non-polyolefinadditives or polymers.

The process preferably begins with extruding a first composition forminga first extrudate, wherein the first composition comprises a firstpolypropylene, a nucleating agent, and a first acid scavenger. The firstcomposition is defined as the composition entering the extruder and thefirst extrudate is defined as the composition exiting the extrusion die.The first composition contains a nucleating agent in an amount of atleast about 50 ppm and the nucleating agent is selected from the groupconsisting of phosphate ester salts, sodium benzoate, lithium benzoate,bis(4-tert-butyl-benzoate)aluminum hydroxide (also known commercially asAI-PTBBA), talc, and compounds conforming to the structure of Formula(I) or Formula (II) illustrated below.

The first extrudate of the invention is useful in producingthermoplastic articles. The first extrudate may be used to create afinished good or resin that may be used in a secondary operation. Thefirst extrudate can be formed into the desired thermoplastic article byany suitable technique, such as injection molding, blow molding (e.g.,injection blow molding or injection stretch blow molding), extrusion,extrusion blow molding, thermoforming, rotomolding, film blowing (blownfilm), film casting (cast film), compression molding and the like. Thefirst extrudate may be biaxially oriented to form a BOPP film (biaxiallyoriented polypropylene), extruded into a fiber, or extruded into a pipeand may also be used as an intermediate resin (pelletized or powdered)that is then feed into another process to create a finished good.

The first extrudate is preferably purposefully nucleated polypropylene,meaning that the nucleating agent is intentionally added to the firstcomposition in an amount great enough to significantly nucleate thefirst polypropylene. As such, the temperature of crystallization (T_(c))will be higher than for the PP in the absence of a nucleating agent.Additionally, the crystalline morphology of the polymer may differ inorientation as dictated by the epitaxial match between the polymer andthe unique nucleating substrate. Intentional loadings of commerciallyavailable nucleating agents may increase the crystallization temperatureof the polymer between 15 and 30° C.

Nucleated polypropylene is highly desired in many markets because of theattributes it brings to the processor and/or end-user. The highercrystallization temperature associated with nucleated polypropylenegenerally translates into faster processing speeds since parts solidifyfaster and at a higher temperature. The reduction in crystal size thatis caused by the nucleating agent also may translate into greatertransparency and gloss. With regard to physical properties, nucleatedpolypropylene generally has higher modulus, greater temperatureresistance, and unique shrinkage properties that are dependent upon thetype of nucleating agent which is being incorporated. In addition,tensile strength may be improved but this may come with a decrease intensile elongation. While these types of properties are generallydesirable, these attributes can be problematic in situations where theseattributes are not desired and where needed accommodations to theprocess cannot be readily made to suit variability in the degree ofnucleation present in the incoming polypropylene composition.

The first polypropylene may be any suitable polypropylene includingpolypropylene homopolymers, polypropylene copolymers (polypropyleneblock copolymers (e.g., impact copolymer), polypropylene randomcopolymers and mini random copolymers), and mixtures thereof. Thecopolymers may contain co-monomers of ethylene, butene, or pentene.

The first composition comprises the nucleating agent in an amount of atleast about 50 ppm of the nucleating agent, more preferably at leastabout 100 ppm. In another embodiment, the first composition comprisesthe nucleating agent in an amount of at least about 300 ppm of thenucleating agent, more preferably at least about 500 ppm. In anotherembodiment, the first composition comprises the nucleating agent in anamount of at least about 1,000 ppm of the nucleating agent, morepreferably at least about 2,000 ppm.

In one embodiment, the nucleating agent is a cycloaliphatic metal salt.In one embodiment, the nucleating agent comprises specific metal saltsof hexahydrophthalic acid (and will be referred to herein as HHPA). Inthis embodiment, the nucleating agent conforms to the structure ofFormula (I):

R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ are either the same ordifferent and are individually selected from the group consisting ofhydrogen, C₁-C₉ alkyl, hydroxy, C₁-C₉ alkoxy, C₁-C₉ alkyleneoxy, amine,and C₁-C₉ alkylamine, halogens, and phenyl. M₁ is a metal or organiccation, x is an integer from 1 to 2, and y is an integer from 1 to 2.Preferably, M₁ is selected from the group of calcium, strontium,lithium, and monobasic aluminum.

In one preferred embodiment, M₁ is a calcium cation and R1-R10 arehydrogen. Ca HHPA as referred to herein refers to Formula (IA). One mayemploy HYPERFORM™ HPN-20E from Milliken & Company of Spartanburg, S.C.which is commercially sold, and comprises Ca HHPA and is described forexample in U.S. Pat. No. 6,599,971 which is hereby incorporated byreference in its entirety.

In another embodiment, the nucleating agent is a bicyclic dicarboxylatemetal salt described, for example, in U.S. Pat. Nos. 6,465,551 and6,534,574. The nucleating agent conforms to the structure of Formula(II):

where M₁₁ and M₁₂ are the same or different, or M₁₁ and M₁₂ are combinedto form a single moiety, and are independently selected from the groupconsisting of metal or organic cations. Preferably, M₁₁ and M₁₂ (or thesingle moiety from the combined M₁₁ and M₁₂) are selected from the groupconsisting of: sodium, calcium, strontium, lithium, zinc, magnesium, andmonobasic aluminum. Wherein R₂₀, R₂₁, R₂₂, R₂₃, R₂₄, R₂₅, R₂₆, R₂₇, R₂₈,and R₂₉ are independently selected from the group consisting of:hydrogen and C₁-C₉ alkyls; and further wherein any two adjacentlypositioned R₂₂-R₂₉ alkyl groups optionally may be combined to form acarbocyclic ring. Preferably, R₂₀-R₂₉ are hydrogen and M₁₁ and M₁₂ are asodium cations.

In particular, suitable bicyclic dicarboxylate metal salts includedisodium bicyclo[2.2.1]heptane-2,3-dicarboxylate, calciumbicyclo[2.2.1]heptane-2,3-dicarboxylate, and combinations thereof. Onemay employ HYPERFORM™ HPN-68 or HPN-68L from Milliken & Company ofSpartanburg, S.C. HPN-68L is commercially sold, and comprises thedisodium bicyclo[2.2.1]heptane-2,3-dicarboxylate shown in Formula (IIA).

In another embodiment, the nucleating agent is a phosphate ester salt.Phosphate ester salts suitable for use as the nucleating and/orclarifying agent include, but are not limited to, sodium2,2′-methylene-bis-(4,6-di-tert-butylphenyl)phosphate (from Asahi DenkaKogyo K. K., known as “NA-11™”), aluminum hydroxybis[2,2′-methylene-bis-(4,6-di-tert-butylphenyl)phosphate] and lithiummyristate (from Asahi Denka Kogyo K. K., known as “NA-21™”), and othersuch phosphate esters such as NA-71 (lithium phosphate salt and lithiumstearate) as disclosed for example in U.S. Pat. Nos. 5,342,868 and4,463,113.

In another embodiment, the nucleating agent is sodium benzoate. When thenucleating agent is sodium benzoate, the sodium benzoate may function asboth the nucleating agent and the acid scavenger and thus a separate andadditional acid scavenger may not need to be employed. In one embodimentwhere the nucleating agent is sodium benzoate, the acid scavenger is thesame composition as the nucleating agent (sodium benzoate).

In another embodiment, the nucleating agent is lithium benzoate. Inanother embodiment, the nucleating agent isbis(4-tert-butyl-benzoate)aluminum hydroxide (also known commercially asAI-PTBBA). In another embodiment, the nucleating agent is talc (hydratedmagnesium silicate).

In certain possibly preferred embodiments, the first compositioncomprises a first acid scavenger in addition to the first polypropyleneand the nucleating agent. The acid scavengers suitable for use in thecomposition of the invention can be any suitable acid scavenger,including but not limited to, aluminum stearate, manganese stearate,calcium stearate, sodium stearate, lithium stearate, magnesium stearate,zinc stearate, cobalt stearate, cerium stearate, potassium stearate,copper stearate, ferric stearate, nickel stearate, calcium lactate,calcium stearoyl lactylate, synthetic hydrotalcites, zinc oxide, calciumoxide, magnesium oxide, and calcium hydroxide. Preferably, the firstacid scavenger is selected from the group consisting of metal salts ofstearic acid, such as calcium stearate, zinc stearate, magnesiumstearate, and mixtures thereof. Calcium stearate may be preferred forsome applications due to its low cost, low coloration, and goodperformance. In another embodiment, the first acid scavenger ishydrotalcite (i.e. DHT-4A) due to its efficacy and low migrationcharacteristics. In one embodiment, the first acid scavenger is a blendof two or more acid scavengers.

When present in the composition, the first acid scavenger can be presentin the first composition in any suitable amount. The level of acidscavenger (first and second) may be chosen based on the nature of thepolymerization catalyst, the amount of residual catalyst, and/or theamount required to effectively stabilize the composition.

Preferably, the first acid scavenger is present in the composition in anamount of about 250 ppm to about 2500 ppm, based on the total weight ofthe first composition. The first acid scavenger is more preferablypresent in the composition in an amount of about 400 ppm to about 1500ppm and most preferably about 500 ppm to about 1200 ppm, based on thetotal weight of the first composition.

Resin extruders will sometimes follow a nucleated polypropylene run witha non-nucleated polypropylene run. In the second step of the process, asecond composition is extruded forming a second extrudate, wherein thesecond composition comprises a second polypropylene and a second acidscavenger, wherein the second extrudate contains less than about 10 ppmof a nucleating agent.

The second polypropylene may be any suitable polypropylene, includingthe polypropylene types disclosed as for the first polypropylene. Thesecond polypropylene may be the same or different polypropylene than thefirst polypropylene.

In one embodiment, the second extrudate contains less than about 5 ppmof the nucleating agent, more preferably less than about 1 ppm. Inanother embodiment, the second extrudate contains less than about 0.1ppm of the nucleating agent, more preferably less than about 0.01 ppm.In another embodiment, the second extrudate contains between about 0.01ppm and 1 ppm of the nucleating agent.

Preferably, no additional nucleating agent is intentionally added to thesecond composition at any point during the preparation and extrusion ofthe second composition. The nucleating agent may be added inadvertentlyto the second composition through residual amounts of nucleating agentretained in the extrusion die/screw/barrel, hoppers, feeders, feedlines, additive masterbatch blenders, or any other part of the extrusionsystem. It has been found that extruded polypropylene containingresidual, low levels of nucleating agent and certain acid scavengers canproduce inadvertently nucleated polypropylene. This nucleation may beundesired and cause undesirable properties in the inadvertentlynucleated polypropylene such as high crystallization temperatures(T_(c)) and difficulty producing BOPP films without tears.

In one embodiment, the content of all nucleating agents in the secondextrudate is less than 10 ppm, more preferably less than 5 ppm, morepreferably less than 1 ppm, more preferably less than 0.1 ppm, morepreferably less than 0.01 ppm.

Preferably, the T_(c) of the second extrudate is within approximately 5°C. of the T_(c) of the second polypropylene uncontaminated baselinestate. The method for determination of this baseline state for a givenpolypropylene is defined in the Test Methods section of thespecification. In another embodiment, the T_(c) of the second extrudateis within approximately 3° C. of the T_(c) of the second polypropyleneuncontaminated baseline state, more preferably within approximately 1.5°C. In another embodiment where the polypropylene comprises homopolymerpolyproylene, the T_(c) of the second extrudate is less than about 115°C., more preferably less than about 112° C., more preferably less thanabout 110° C.

Preferably, the difference between the Tc of the first extrudate and thesecond extrudate is greater than approximately 5° C., more preferablygreater than approximately 10° C., even more preferably betweenapproximately 15 and 20° C. and most preferably greater thanapproximately 25° C.

Without being bound to any single theory, it is hypothesized that thepreferred second acid scavengers are thought to be de-activating theresidual amounts of nucleator. This de-activation may be enabled throughan ion-exchange mechanism between the residual nucleator and the acidneutralizer; thereby, changing the chemical nature of the nucleatingspecies. This de-activation may also occur by the acid neutralizercoating the surface of the nucleator, thereby altering the epitaxialmatch between the nucleator and the polypropylene.

In one embodiment, the second acid scavenger is a potassium salt of afatty acid. It has been found that the potassium salt of a fatty acidresults in low nucleation of a polypropylene with all known nucleatingagents described above and the like. Preferably, the second acidscavenger comprises a potassium cation and a C₃-C₂₂ fatty acid anion.More preferably, the second acid scavenger comprises potassium stearate.In one embodiment, the second acid scavenger is a blend of two or moreacid scavengers.

In the embodiment where the nucleating agent is a compositioncorresponding to Formula (I), then the second acid scavenger ispreferably a metal salt of a fatty acid, wherein the metal saltcomprises a cation of a metal selected from the group consisting oflithium, sodium, potassium, and magnesium. In one embodiment, the secondacid scavenger contains a potassium or sodium cation and a C₃-C₂₂ fattyacid anion. In one embodiment, the second acid scavenger contains alithium or magnesium cation and a C₃-C₂₂ fatty acid anion. In apreferred embodiment, the second acid scavenger is potassium stearate.In another preferred embodiment, the second acid scavenger is sodiumstearate. It has been found that potassium stearate and sodium stearateare able to prevent or significantly reduce any unwanted nucleation ofpolypropylene extrudates having low amounts of residual nucleatingagents corresponding to Formula (I). In one embodiment, the second acidscavenger is a blend of two or more acid scavengers. In one embodiment,the second acid scavenger is selected from the group consisting oftitanium dioxide, calcium silicate, and silica.

In the embodiment where the nucleating agent is a compositioncorresponding to Formula (II), then the second acid scavenger isselected from the group consisting metal stearoyl-2-lactylate,wollastonite (CaSiO₃), and magnesium oxysulfate, silica, and a metalsalt of a fatty acid, wherein the metal salt comprises a cation of ametal selected from the group consisting of aluminum, manganese, zinc,potassium, and magnesium. In one embodiment, the second acid scavengercontains a potassium or aluminum cation and a C₃-C₂₂ fatty acid anion.In a preferred embodiment, the second acid scavenger is potassiumstearate. In another preferred embodiment, the second acid scavenger isaluminum stearate. It has been found that potassium stearate andaluminum stearate are able to prevent or significantly reduce anyunwanted nucleation of polypropylene extrudates having low amounts ofresidual nucleating agents corresponding to Formula (II). In anotherpreferred embodiment, the second acid scavenger may be calcium stearoyllactylate, zinc 12-hydroxy stearate or magnesium 12-hydroxy stearate. Inone embodiment, the second acid scavenger is a blend of two or more acidscavengers.

In the embodiment where the nucleating agent is a phosphate ester salt,sodium benzoate, lithium benzoate, bis(4-tert-butyl-benzoate)aluminumhydroxide (commercially known as AI-ptbba), talc, then the second acidscavenger is preferably a metal salt of a fatty acid, wherein the metalsalt comprises a cation of a metal is selected from the group consistingof sodium, aluminum, and potassium. In one embodiment, the second acidscavenger is a blend of two or more acid scavengers.

In one embodiment, the first acid scavenger and the second acidscavenger are the same composition. This may be preferred inmanufacturing environments to lower costs and simplify raw materialstreams.

The process may be used to form polypropylene finished goods or resinshaving significantly reduced undesired nucleation due to residualamounts of nucleating agents. In one embodiment, the biaxially orientedpolypropylene film may be produced. In this specification, biaxiallyoriented polypropylene film is defined to include oriented polymer filmssuch as tentered or blown polypropylene films.

In one embodiment, the BOPP film comprises a nucleating agent, apotassium salt of a fatty acid and a thermoplastic essentiallyconsisting of polypropylene. The content of all nucleating agents in thefilm is less than 10 ppm, and wherein the nucleating agent preferablyconforms to the structure of Formula (I) or (II). The film may containone or more layers and at least one of the layers contains a nucleatingagent, a potassium salt of a fatty acid, and thermoplastic essentiallyconsisting of polypropylene, wherein the content of all nucleatingagents in the film is less than 10 ppm, and wherein the nucleating agentconforms to the structure of Formula (I) or (II). Preferably, all of thethermoplastic polymer within the film essentially consists ofpolypropylene. In this application, “essentially consisting ofpolypropylene” means that the polypropylene polymer contains less than10% by weight of other thermoplastic polymers.

Test Methods

Peak Crystallization Temperature (T_(c))—The peak crystallizationtemperature (T_(c)) for all examples was determined in accordance withASTM D3418-08, modified with a profile of heating from 50° C. to 220° C.at a rate of 20° C./min, holding for 2 minutes, and cooling at a rate of20° C./min back to 50° C. Under these conditions, the peak T_(c) wasthen determined from the crystallization exotherm. Two instruments wereinvolved in the measurement of samples—a Mettler Toledo DSC 822 andMettler Toledo DSC 1 Star. The T_(c) bias between the 2 instruments wasapproximately 1° C.

Baseline T_(c)—The baseline value of 107.5° C. was established by a)making a 0.5 kg batch consisting of PRO-FAX™ 6301 reactor flake, 500 ppmof IRGANOX™ 1010, 1000 ppm of IRGAFOS™ 168, and 500 ppm of calciumstearate, b) vigorously mixing the batch in a sterile plastic bag, c)molding the powder mixture into discs having a thickness of 1.27 mm witha Carver Press exerting a hydraulic pressure of 13,000 psi and atemperature of 230° C., d) obtaining specimens from these discs fordifferential scanning calorimetry, and e) determining the peakcrystallization temperature (T_(c)) in accordance with ASTM D3418-08(modified with a profile of heating from 50° C. to 220° C. at a rate of20° C./min, holding for 2 minutes, and cooling at a rate of 20° C./minback to 50° C.) whereby the peak T_(c) value was determined from thecrystallization exotherm. In this manner, the T_(c) was determined fromthe polymer having a standard additive package whereby the risk ofintroducing contaminants capable of nucleating the polymer could beessentially eliminated.

Example Set 1

Some polypropylene extrusion systems first extrude a polypropylene witha nucleating agent (in an amount greater than 50 ppm), then switch overto a non-nucleated grade polypropylene. The non-nucleated gradepolypropylene may still contain residual amounts (1 ppm) of nucleatingagent. This example simulates the non-nucleated grade polypropylene withresidual amounts of nucleating agent and the effect of various acidscavengers on the T_(c) of the polypropylene composition.

To create polypropylene compositions having low levels of nucleatingagents, a concentrated nucleating agent mixture was first formed byadding the following ingredients to PRO-FAX™ 6301 12 MFR PP homopolymerreactor flake: IRGANOX™ 1010 in an amount of 500 ppm, IRGAFOS™ 168 in anamount of 1000 ppm, and HYPERFORM™ HPN-68L (abbreviated in thisapplication as HPN-68L) available from MILLIKEN & COMPANY™ or HYPERFORM™HPN-20E (abbreviated in this application as HPN-20E) available fromMILLIKEN & COMPANY™ nucleator in an amount of 1000 ppm. Utilizing a 1 kgbatch size, these ingredients were high intensity blended in a 10 literHENSCHEL™ mixer for 1 minute forming the concentrated nucleating agentmixture.

Next, to a reactor flake of a polypropylene homopolymer used formanufacturing bi-axially oriented polypropylene film, the followingingredients were added: IRGANOX™ 1010 in an amount of 500 ppm, IRGAFOS™168 in an amount of 1000 ppm, and the concentrated nucleating agentmixture in an amount of 1000 ppm. This serial dilution resulted inapproximately 1 ppm nucleating agent in the formulation. In addition,the acid scavenger to be screened was also added at a concentrationconsistent with its use in commercial formulations. Utilizing a 0.5 kgbatch size, these ingredients were high intensity blended in a 4 literHENSCHEL™ mixer for 1 minute.

The diluted formulations were then compounded on a DELTAPLAST™ extruder(typical output of approximately 6 kg/hr) having a 25 mm single screwwith an L/D ratio of 30:1 and equipped with a Maddocks mixer. The barreltemperature profile was set with a maximum zone setting of approximately230° C. The molten polymer was filtered through a 60 mesh screen packand then extruded through a strand die. The strand was subsequentlyquenched in a water bath, dried, and pelletized.

The extruded pellets were molded into discs having a thickness of 1.27mm with a Carver Press exerting a hydraulic pressure of 13,000 psi and atemperature of 230° C. Specimens were taken from these discs fordifferential scanning calorimetry.

TABLE 1 Nucleating agent loading, acid scavenger loading, and peak T_(c)for Examples 1-4. Nucleating Agent Acid Scavenger Loading Loading PeakHPN- HPN- Potassium Sodium Aluminum T_(c) 20E 68L Stearate StearateStearate (° C.) Example 1 1 ppm — 500 ppm — — 105.8 Example 2 1 ppm — —500 ppm — 109.2 Example 3 — 1 ppm 500 ppm — 107.5 Example 4 — 1 ppm 500ppm 106.3

The baseline T_(c) of the polypropylene used for manufacturingbi-axially oriented film was 107.3° C. As can be seen from the resultsset forth in the Table 1, the T_(c) of Examples 1-4 were within +/−2° C.of the BOPP grade polypropylene. These data illustrate that the harmfuleffects (i.e. T_(c) values 5-10° C. over baseline) from residual amountsof HPN-20E and HPN-68L can be essentially eliminated through theselection of preferred acid scavengers. The baseline (for only ExampleSet 1) was not measured in the manner described in the Test Methodssection. This baseline value of 107.3° C. was established by a) making a0.1 kg batch consisting of the subject polypropylene reactor flake, 500ppm of Irganox 1010, 1000 ppm of Irganox 1010, and 500 ppm of calciumstearate, b) vigorously mixing the batch in a sterile plastic bag, c)molding the powder mixture into discs having a thickness of 1.27 mm witha Carver Press exerting a hydraulic pressure of 13,000 psi and atemperature of 230° C., d) obtaining specimens from these discs fordifferential scanning calorimetry, and e) determining the peakcrystallization temperature (T_(c)) in accordance with ASTM D3418-08(modified with a profile of heating from 50° C. to 220° C. at a rate of20° C./min, holding for 2 minutes, and cooling at a rate of 20° C./minback to 50° C.) whereby the peak T_(c) value was determined from thecrystallization exotherm. In this manner, the T_(c) was determined fromthe polymer having a standard additive package whereby the risk ofintroducing contaminants capable of nucleating the polymer could beessentially eliminated.

Example Set 2

To illustrate how quickly a preferred acid neutralizer could diminishthe unwanted effects from residual nucleation, an experiment wasdesigned on a DELTAPLAST™ 25 mm single screw extruder (30:1 l/d)equipped with a MADDOCKS™ mixer (typical output of approximately 6kg/hr). The barrel temperature profile was set with a maximum zonesetting of approximately 230° C. The molten polymer was filtered througha 60 mesh screen pack and then extruded through a strand die. The strandwas subsequently quenched in a water bath, dried, and pelletized.

Prior to extrusion, all samples were pre-blended on a 10 liter HENSCHEL™high intensity mixer for 1 minute. Before introducing the samples intothe extruder, the extruder was purged with 5 kg of a commercialnon-nucleated 1.8 MFR polypropylene homopolymer.

Following the 5 kg purge, a 1 kg nucleated “contamination” batch wasextruded into strands that were subsequently water-cooled and choppedinto pellets. This batch consisted of PRO-FAX™ 6301 homopolymer with thefollowing additive package: IRGANOX™ 1010—500 ppm, IRGAFOS™ 168—1000ppm, DHT-4A—400 ppm, and HPN-20E—400 ppm.

The extruded pellets from the “contamination” batch were molded intodiscs having a thickness of 1.27 mm with a Carver Press exerting ahydraulic pressure of 13,000 psi and a temperature of 230° C. Specimenswere taken from these discs for differential scanning calorimetry.

Immediately following the “contamination” batch, a compound was extrudedfor 90 minutes that consisted of PRO-FAX™ 6301 homopolymer and thefollowing additive package: IRGANOX™ 1010—500 ppm, IRGAFOS™ 168—1000ppm, and sodium stearate—500 ppm forming Example 7.

Extruded pellet samples were collected after 1, 15, 30, 45, 60, 75, and90 minutes. The extruded pellets were molded into discs having athickness of 1.27 mm with a Carver Press exerting a hydraulic pressureof 13,000 psi and a temperature of 230° C. Specimens were taken fromthese discs for differential scanning calorimetry to determine the peakcrystallization temperature (T_(c)).

The steps in Example Set 2 were repeated with the exception that calciumstearate was substituted for sodium stearate forming Example 6. Thesteps in Example Set 2 were repeated with the exception that DHT-4A (asynthetic hydrotalcite) was substituted for sodium stearate formingExample 5.

As seen from FIG. 1, the T_(c) of the formulation of Example 7(containing the sodium stearate) drops almost immediately to baseline ofthe polypropylene (107.5° C.) and is 5-8° C. lower than Examples 5 and 6that contained the commonly used acid neutralizers, DHT-4A and calciumstearate. For the remaining 89 minutes of the test, Example 5 (DHT-4A)appeared to plateau around 115° C. while only a modest reduction wasobserved in Example 6 (CaSt). Examples 5 and 6 typify the problem ofridding an extrusion system of nucleator to enable truly non-nucleatedcrystallization values to be attained. On the other hand, by a mechanismwhich is not fully understood, the sodium stearate (Example 7)apparently deactivates the residual amounts of the HPN-20E remaining inthe system.

Example Set 3

Some polypropylene extrusion systems first extrude a polypropylene witha nucleating agent (in an amount greater than 50 ppm), then switch overto a non-nucleated grade polypropylene. The non-nucleated gradepolypropylene may still contain residual amounts (1 ppm) of nucleatingagent. This example simulates the non-nucleated grade polypropylene withresidual amounts of various commercially available nucleating agents andthe effects of various preferred acid scavengers on the T_(c) of thepolypropylene composition.

To create polypropylene compositions having low levels of nucleatingagents, a concentrated nucleating agent mixture was first formed byadding the following ingredients to PRO-FAX™ 6301 12 MFR PP homopolymerreactor flake: IRGANOX™ 1010 in an amount of 500 ppm, IRGAFOS™ 168 in anamount of 1000 ppm, and nucleator (either FLUID ENERGY™ sodium benzoate,ASAHI DENKA™ NA-11, ASAHI DENKA™ NA-21, ASAHI DENKA™ NA-71, GCH aluminump-tertiary butyl benzoic acid (also known as AI-PTBBA and alsobis(4-tert-butyl-benzoate)aluminum hydroxide), IMERYS™ Jetfine 3CA talc,or SIGMA ALDRICH™ lithium benzoate) in an amount of 1000 ppm. Utilizinga 0.5 kg batch size, these ingredients were high intensity blended in a4 liter Henschel mixer for 1 minute forming the concentrated nucleatingagent mixture.

Next, to PRO-FAX™ 6301 12 MFR PP homopolymer reactor flake, thefollowing ingredients were added: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and the concentrated nucleatingagent mixture in an amount of 1000 ppm. This serial dilution resulted in1 ppm nucleating agent in the formulation. In addition, the acidscavenger to be screened was also added at a concentration consistentwith its use in commercial formulations. Utilizing a 0.5 kg batch size,these ingredients were high intensity blended in a 4 liter HENSCHEL™mixer for 1 minute.

The diluted formulations were then compounded on a DELTAPLAST™ extruder(typical output of approximately 6 kg/hr) having a 25 mm single screwwith an L/D ratio of 30:1 and equipped with a MADDOCKS™ mixer. Thebarrel temperature profile was set with a maximum zone setting ofapproximately 230° C. The molten polymer was filtered through a 60 meshscreen pack and then extruded through a strand die. The strand wassubsequently quenched in a water bath, dried, and pelletized.

The extruded pellets were molded into discs having a thickness of 1.27mm with a Carver Press exerting a hydraulic pressure of 13,000 psi and atemperature of 230° C. Specimens were taken from these discs fordifferential scanning calorimetry to determine the peak crystallizationtemperature (T_(c))

TABLE 2 Nucleating agent loading, acid scavenger loading, and peak T_(c)of Examples 8-28 Potassium Sodium Aluminum Peak Stearate StearateStearate Tc Nucleator Loading Loading Loading Loading (° C.) Example 8Sodium Benzoate 500 ppm — — 105.8 1 ppm Example 9 Sodium Benzoate — 500ppm — 107.0 1 ppm Example 10 Sodium Benzoate — — 500 ppm 106.0 1 ppmExample 11 Asahi Denka 500 ppm — — 106.0 NA-11 1 ppm Example 12 AsahiDenka — 500 ppm — 112.3 NA-11 1 ppm Example 13 Asahi Denka — — 500 ppm105.8 NA-11 1 ppm Example 14 Asahi Denka 500 ppm — — 104.7 NA-21 1 ppmExample 15 Asahi Denka — 500 ppm — 108.0 NA-21 1 ppm Example 16 AsahiDenka — — 500 ppm 105.8 NA-21 1 ppm Example 17 Asahi Denka 500 ppm — —104.8 NA-71 1 ppm Example 18 Asahi Denka — 500 ppm — 109.3 NA-71 1 ppmExample 19 Asahi Denka — — 500 ppm 105.3 NA-71 1 ppm Example 20 Aluminum500 ppm — — 104.5 p-tertiary butyl benzoic acid 1 ppm Example 21Aluminum — 500 ppm — 106.3 p-tertiary butyl benzoic acid 1 ppm Example22 Aluminum — — 500 ppm 105.7 p-tertiary butyl benzoic acid 1 ppmExample 23 Talc 1 ppm 500 ppm — — 108.2 Example 24 Talc 1 ppm — 500 ppm— 109.0 Example 25 Talc 1 ppm — — 500 ppm 107.8 Example 26 LithiumBenzoate 500 ppm — — 105.3 1 ppm Example 27 Lithium Benzoate — 500 ppm —107.0 1 ppm Example 28 Lithium Benzoate — — 500 ppm 104.5 1 ppm

Reviewing Examples 8-28, each Example when used in conjunction withresidual amounts of various nucleators resulted in imparted T_(c) valuesthat were either below baseline or no more than about 5° C. abovebaseline. Examples 8-11 and 13-28 when used in conjunction with residualamounts of various nucleators resulted in an imparted T_(c) values thatwere either below baseline or no more than about 2° C. above baseline.Therefore, it appears that the preferred stearates would have broadapplicability for use in non-nucleated polypropylene where baselineT_(c) performance is desired.

Example Set 4

Some polypropylene extrusion systems first extrude a polypropylene witha nucleating agent (in an amount greater than 50 ppm), then switch overto a non-nucleated grade polypropylene. The non-nucleated gradepolypropylene may still contain residual amounts (1 ppm) of nucleatingagent. This example simulates the non-nucleated grade polypropylene withresidual amounts of HPN-20E and the effects of various acid scavengersfrom the class comprising metallic salts of stearic acid.

To create the polypropylene compositions having low levels of HPN-20Enucleating agent, a concentrated nucleating agent mixture was firstformed by adding the following ingredients to PRO-FAX™ 6301 12 MFR PPhomopolymer reactor flake: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and HPN-20E nucleator in anamount of 1000 ppm. Utilizing a 0.5 kg batch size, these ingredientswere high intensity blended in a 4 liter HENSCHEL™ mixer for 1 minuteforming the concentrated HPN-20E nucleating agent mixture.

Next, to PRO-FAX™ 6301 12 MFR PP homopolymer reactor flake, thefollowing ingredients were added: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and the concentrated nucleatingagent mixture in an amount of 1000 ppm. This serial dilution resulted in1 ppm of HPN-20E nucleating agent in the formulation. In addition, theacid scavenger to be screened was also added at a concentrationconsistent with its use in commercial formulations. Utilizing a 0.5 kgbatch size, these ingredients were high intensity blended in a 4 literHENSCHEL™ mixer for 1 minute.

The diluted formulations were then compounded on a DELTAPLAST™ extruder(typical output of approximately 6 kg/hr) having a 25 mm single screwwith an L/D ratio of 30:1 and equipped with a MADDOCKS™ mixer. Thebarrel temperature profile was set with a maximum zone setting ofapproximately 230° C. The molten polymer was filtered through a 60 meshscreen pack and then extruded through a strand die. The strand wassubsequently quenched in a water bath, dried, and pelletized.

The extruded pellets were molded into discs having a thickness of 1.27mm with a Carver Press exerting a hydraulic pressure of 13,000 psi and atemperature of 230° C. Specimens were taken from these discs fordifferential scanning calorimetry to determine the peak crystallizationtemperature (T_(c)).

TABLE 3 Nucleating agent loading, acid scavenger loading, and peak T_(c)for Examples 29-48 Peak T_(c) Nucleator Loading Acid Neutralizer Loading(° C.) Example 29 HPN-20E 1 ppm Li Stearate 500 ppm 110.7 Example 30HPN-20E 1 ppm Na Stearate 500 ppm 111.0 Example 31 HPN-20E 1 ppm KStearate 500 ppm 107.6 Example 32 HPN-20E 1 ppm Mg Stearate 500 ppm115.3 Example 33 HPN-20E 1 ppm Ca Stearate 500 ppm 116.2 Example 34HPN-20E 1 ppm Mn Stearate 500 ppm 115.7 Example 35 HPN-20E 1 ppm CoStearate 500 ppm 116.7 Example 36 HPN-20E 1 ppm Cu Stearate 500 ppm117.3 Example 37 HPN-20E 1 ppm Zn Stearate 500 ppm 116.7 Example 38HPN-20E 1 ppm Ba Stearate 500 ppm 116.8 Example 39 HPN-20E 1 ppm AlStearate 500 ppm 115.3 Example 40 HPN-20E 1 ppm La Stearate 500 ppm116.5 Example 41 HPN-20E 1 ppm Li 12-hydroxy stearate 116.8 500 ppmExample 42 HPN-20E 1 ppm Mg 12-hydroxy stearate 112.8 500 ppm Example 43HPN-20E 1 ppm Ca 12-hydroxy stearate 117.0 500 ppm Example 44 HPN-20E 1ppm Zn 12-hydroxy stearate 114.7 500 ppm Example 45 HPN-20E 1 ppm CaStearoyl Lactylate 116.3 (Pationic 930) Example 46 HPN-20E 1 ppm CaStearoyl Lactylate 117.7 overbased with Ca(OH)₂ (Pationic 940) Example47 HPN-20E 1 ppm Ca Lactate (Pationic 1230) 116.5 Example 48 HPN-20E 1ppm Ca Lactate overbased with 117.5 Ca(OH)₂ (Pationic 1240)

In general, the monovalent metal salts of stearic acid (examples 29-31)produced the lowest peak crystallization temperatures when used inconjunction with residual amounts of HPN-20E, imparting T_(c) valuesthat were within about 3.5° C. above the baseline. Among these types,the potassium stearate provided the lowest Tc response. In this ExampleSet, no significant differences in the above examples were apparentbetween the divalent and trivalent salts that were tested.

Example Set 5

Some polypropylene extrusion systems first extrude a polypropylene witha nucleating agent (in an amount greater than 50 ppm), then switch overto a non-nucleated grade polypropylene. The non-nucleated gradepolypropylene may still contain residual amounts (1 ppm) of nucleatingagent. This example simulates the non-nucleated grade polypropylene withresidual amounts of HPN-68L and the effects of various acid scavengersfrom the class comprising metallic fatty acid salts.

To create the polypropylene compositions having low levels of HPN-68Lnucleating agent, a concentrated nucleating agent mixture was firstformed by adding the following ingredients to PRO-FAX™ 6301 12 MFR PPhomopolymer reactor flake: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and HPN-68L nucleator in anamount of 1000 ppm. Utilizing a 0.5 kg batch size, these ingredientswere high intensity blended in a 4 liter HENSCHEL™ mixer for 1 minuteforming the concentrated HPN-68L nucleating agent mixture.

Next, to PRO-FAX™ 6301 12 MFR PP homopolymer reactor flake, thefollowing ingredients were added: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and the concentrated nucleatingagent mixture in an amount of 1000 ppm. This serial dilution resulted in1 ppm of HPN-68L nucleating agent in the formulation. In addition, theacid scavenger to be screened was also added at a concentrationconsistent with its use in commercial formulations. Utilizing a 0.5 kgbatch size, these ingredients were high intensity blended in a 4 literHENSCHEL™ mixer for 1 minute.

The diluted formulations were then compounded on a DELTAPLAST™ extruder(typical output of approximately 6 kg/hr) having a 25 mm single screwwith an L/D ratio of 30:1 and equipped with a MADDOCKS™ mixer. Thebarrel temperature profile was set with a maximum zone setting ofapproximately 230° C. The molten polymer was filtered through a 60 meshscreen pack and then extruded through a strand die. The strand wassubsequently quenched in a water bath, dried, and pelletized.

The extruded pellets were molded into discs having a thickness of 1.27mm with a Carver Press exerting a hydraulic pressure of 13,000 psi and atemperature of 230° C. Specimens were taken from these discs fordifferential scanning calorimetry to determine the peak crystallizationtemperature (T_(c)).

TABLE 4 Nucleating agent loading, acid scavenger loading, and peak T_(c)of Examples 49-68. Peak T_(c) Nucleator Loading Acid Neutralizer Loading(° C.) Example 49 HPN-68L 1 ppm Li Stearate 500 ppm 117.3 Example 50HPN-68L 1 ppm Na Stearate 500 ppm 117.6 Example 51 HPN-68L 1 ppm KStearate 500 ppm 109.5 Example 52 HPN-68L 1 ppm Mg Stearate 500 ppm111.5 Example 53 HPN-68L 1 ppm Ca Stearate 500 ppm 117.2 Example 54HPN-68L 1 ppm Mn Stearate 500 ppm 110.2 Example 55 HPN-68L 1 ppm CoStearate 500 ppm 113.5 Example 56 HPN-68L 1 ppm Cu Stearate 500 ppm114.3 Example 57 HPN-68L 1 ppm Zn Stearate 500 ppm 111.3 Example 58HPN-68L 1 ppm Ba Stearate 500 ppm 116.2 Example 59 HPN-68L 1 ppm AlStearate 500 ppm 109.0 Example 60 HPN-68L 1 ppm La Stearate 500 ppm113.2 Example 61 HPN-68L 1 ppm Li 12-hydroxy stearate 116.8 500 ppmExample 62 HPN-68L 1 ppm Mg 12-hydroxy stearate 107.5 500 ppm Example 63HPN-68L 1 ppm Ca 12-hydroxy stearate 117.2 500 ppm Example 64 HPN-68L 1ppm Zn 12-hydroxy stearate 108.0 500 ppm Example 65 HPN-68L 1 ppm CaStearoyl Lactylate 109.2 (Pationic 930) 500 ppm Example 66 HPN-68L 1 ppmCa Stearoyl Lactylate 117.8 overbased with Ca(OH)₂ (Pationic 940) 500ppm Example 67 HPN-68L 1 ppm Ca Lactate (Pationic 1230) 115.0 500 ppmExample 68 HPN-68L 1 ppm Ca Lactate overbased with 116.3 Ca(OH)₂(Pationic 1240) 500 ppm

No correlation appeared to exist between the valency of the metallicstearate and peak crystallization temperature when the salt was used inconjunction with residual amounts of Hyperform HPN-68L. In fact lowT_(c) values were observed with the monovalent potassium salt (example51); divalent magnesium, manganese, and zinc salts (examples 52, 54, 57respectively); and the trivalent aluminum salt (example 59). All ofthese previously mentioned salts imparted T_(c) values that were withinabout 3.8° C. above baseline.

Potassium stearate (examples 31 and 51) provides a low Tc response witheither HPN-68L or HPN-20E and is preferred. With respect to the12-hydroxy stearates (examples 61-64), the magnesium and zinc saltsprovided Tc values within about 0.5° C. above baseline.

With respect to the calcium lactates and lactylates (examples 65-68),none provided the desirable low peak crystallization temperature in thepresence of residual amounts of HPN-68L nucleator except for the calciumstearoyl lactylate (Pationic 930). This acid neutralizer is the only Casalt that has provided a low crystallization temperature in the presenceof either HPN-20E or HPN-68L.

Except for potassium stearate, all of the stearates tested seem to havediffering responses when used with residual amounts of HPN-68L versusHPN-20E with respect to the peak crystallization temperature of the PPcomposition.

Example Set 6

Some polypropylene extrusion systems first extrude a polypropylene witha nucleating agent (in an amount greater than 50 ppm), then switch overto a non-nucleated grade polypropylene. The non-nucleated gradepolypropylene may still contain residual amounts (1 ppm) of nucleatingagent. This example simulates the non-nucleated grade polypropylene withresidual amounts of HPN-20E and the effects of various inorganicadditives and acid scavengers.

To create the polypropylene compositions having low levels of HPN-20Enucleating agent, a concentrated nucleating agent mixture was firstformed by adding the following ingredients to PRO-FAX™ 6301 12 MFR PPhomopolymer reactor flake: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and HPN-20E nucleator in anamount of 1000 ppm. Utilizing a 0.5 kg batch size, these ingredientswere high intensity blended in a 4 liter HENSCHEL™ mixer for 1 minuteforming the concentrated HPN-20E nucleating agent mixture.

Next, to PRO-FAX™ 6301 12 MFR PP homopolymer reactor flake, thefollowing ingredients were added: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and the concentrated nucleatingagent mixture in an amount of 1000 ppm. This serial dilution resulted in1 ppm of HPN-20E nucleating agent in the formulation. In addition, theinorganic additives and acid scavengers to be screened were all added ata concentration of 1000 ppm. Utilizing a 0.5 kg batch size, theseingredients were high intensity blended in a 4 liter HENSCHEL™ mixer for1 minute.

The diluted formulations were then compounded on a DELTAPLAST™ extruder(typical output of approximately 6 kg/hr) having a 25 mm single screwwith an L/D ratio of 30:1 and equipped with a MADDOCKS™ mixer. Thebarrel temperature profile was set with a maximum zone setting ofapproximately 230° C. The molten polymer was filtered through a 60 meshscreen pack and then extruded through a strand die. The strand wassubsequently quenched in a water bath, dried, and pelletized.

The extruded pellets were molded into discs having a thickness of 1.27mm with a Carver Press exerting a hydraulic pressure of 13,000 psi and atemperature of 230° C. Specimens were taken from these discs fordifferential scanning calorimetry to determine the peak crystallizationtemperature (T_(c)).

TABLE 5 Nucleating agent loading, additive/acid scavenger loading, andpeak T_(c) of Examples 69-78. Nucleator Inorganic Additive/Acid PeakT_(c) Loading Neutralizer Loading (° C.) Example 69 HPN-20E Magnesiumoxysulfate-1000 ppm 115.7 1 ppm (Milliken Hyperform HPR-803i) Example 70HPN-20E Magnesium Oxide-1000 ppm 117.2 1 ppm (Sigma Aldrich) Example 71HPN-20E Magnesium Dihydroxide-1000 ppm 116.5 1 ppm (Huber Vertex 60HST)Example 72 HPN-20E Calcium Oxide-1000 ppm 118.2 1 ppm (Polycal OS325)Example 73 HPN-20E USP Zinc Oxide-1000 ppm 117.2 1 ppm (ZCA USP) Example74 HPN-20E Titanium dioxide-1000 ppm 114.3 1 ppm (TR-23) Example 75HPN-20E Calcium carbonate-1000 ppm 116.3 1 ppm (Imerys Supercoat)Example 76 HPN-20E Calcium Silicate-1000 ppm 114.0 1 ppm (NYCO Nyglos 8)Example 77 HPN-20E Silica-1000 ppm 113.2 1 ppm (WR Grace Perkasil SM660)Example 78 HPN-20E Synthetic Hydrotalcite-1000 ppm 118.4 1 ppm (KyowaDHT-4A)

As can be seen in Table 5, some inorganic additives are also effectiveat reducing the T_(c) in the presence of residual amounts of the HPN-20Enucleator. Some of the higher performers (i.e., titanium dioxide,calcium silicate, and silica, examples 74, 76, and 77 respectively) were5.7-6.8° C. above the polypropylene baseline crystallizationtemperature.

Example Set 7

Some polypropylene extrusion systems first extrude a polypropylene witha nucleating agent (in an amount greater than 50 ppm), then switch overto a non-nucleated grade polypropylene. The non-nucleated gradepolypropylene may still contain residual amounts (1 ppm) of nucleatingagent. This example simulates the non-nucleated grade polypropylene withresidual amounts of HPN-68L and the effects of various inorganicadditives and acid scavengers.

To create the polypropylene compositions having low levels of HPN-68Lnucleating agent, a concentrated nucleating agent mixture was firstformed by adding the following ingredients to PRO-FAX™ 6301 12 MFR PPhomopolymer reactor flake: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and HPN-68L nucleator in anamount of 1000 ppm. Utilizing a 0.5 kg batch size, these ingredientswere high intensity blended in a 4 liter HENSCHEL™ mixer for 1 minuteforming the concentrated HPN-68L nucleating agent mixture.

Next, to PRO-FAX™ 6301 12 MFR PP homopolymer reactor flake, thefollowing ingredients were added: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and the concentrated nucleatingagent mixture in an amount of 1000 ppm. This serial dilution resulted in1 ppm of HPN-68L nucleating agent in the formulation. In addition, theinorganic additives and acid scavengers to be screened were all added ata concentration of 1000 ppm. Utilizing a 0.5 kg batch size, theseingredients were high intensity blended in a 4 liter HENSCHEL™ mixer for1 minute.

The diluted formulations were then compounded on a DELTAPLAST™ extruder(typical output of approximately 6 kg/hr) having a 25 mm single screwwith an L/D ratio of 30:1 and equipped with a Maddocks mixer. The barreltemperature profile was set with a maximum zone setting of approximately230° C. The molten polymer was filtered through a 60 mesh screen packand then extruded through a strand die. The strand was subsequentlyquenched in a water bath, dried, and pelletized.

The extruded pellets were molded into discs having a thickness of 1.27mm with a Carver Press exerting a hydraulic pressure of 13,000 psi and atemperature of 230° C. Specimens were taken from these discs fordifferential scanning calorimetry to determine the peak crystallizationtemperature (T_(c)).

TABLE 6 Nucleating agent loading, additive/acid scavenger loading, andpeak T_(c) in Examples 79-88. Nucleator Inorganic Additive/Acid PeakT_(c) Loading Neutralizer Loading (° C.) Example 79 HPN-68L Magnesiumoxysulfate-1000 ppm 112.2 1 ppm (Milliken Hyperform HPR-803i) Example 80HPN-68L Magnesium Oxide-1000 ppm 114.7 1 ppm (Sigma Aldrich) Example 81HPN-68L Magnesium Dihydroxide-1000 ppm 113.7 1 ppm (Huber Vertex 60HST)Example 82 HPN-68L Calcium Oxide-1000 ppm 116.0 1 ppm (Polycal OS325)Example 83 HPN-68L USP Zinc Oxide-1000 ppm 114.2 1 ppm (ZCA USP) Example84 HPN-68L Titanium dioxide-1000 ppm 110.2 1 ppm (TR-23) Example 85HPN-68L Calcium carbonate-1000 ppm 113.7 1 ppm (Imerys Supercoat)Example 86 HPN-68L Calcium Silicate-1000 ppm 108.8 1 ppm (NYCO Nyglos 8)Example 87 HPN-68L Silica-1000 ppm 111.8 1 ppm (WR Grace Perkasil SM660)Example 88 HPN-68L Synthetic Hydrotalcite-1000 ppm 119.5 1 ppm (KyowaDHT-4A)

In the presence of residual amounts of HPN-68L nucleator, calciumsilicate (example 86) and titanium dioxide (example 84) strongly reducethe peak crystallization value. In these cases, both were within about2.7° C. above the polypropylene baseline crystallization temperature.Similarly, magnesium oxysulfate (example 79) and silica (example 87)were found to provide suppressed peak crystallization values that werewithin about 4.7° C. above the polypropylene baseline crystallizationtemperature.

Example Set 8

Previous studies have shown that potassium stearate imparts a preferredlow peak crystallization value in the presence of residual amounts ofboth HPN-20E and HPN-68L. On the other hand, calcium stearateconsistently imparted an undesirably high peak crystallization value inthe presence of residual amounts of both HPN-20E and HPN-68L. This studywas undertaken to understand if the carbon chain length would affect thebehavior of either the potassium or calcium fatty acid salt.

To create the polypropylene compositions having low levels of HyperformHPN-68L nucleating agent, a concentrated nucleating agent mixture wasfirst formed by adding the following ingredients to PRO-FAX™ 6301 12 MFRPP homopolymer reactor flake: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and HPN-68L nucleator in anamount of 1000 ppm. Utilizing a 0.5 kg batch size, these ingredientswere high intensity blended in a 4 liter HENSCHEL™ mixer for 1 minuteforming the concentrated HPN-68L nucleating agent mixture.

Next, to PRO-FAX™ 6301 12 MFR PP homopolymer reactor flake, thefollowing ingredients were added: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and the concentrated nucleatingagent mixture in an amount of either 500 ppm or 1000 ppm. In addition,the acid scavenger to be screened was also added at a concentrationconsistent with its use in commercial formulations. This serial dilutionresulted in either 0.5 ppm or 1 ppm of HPN-68L nucleating agent in theformulation. Utilizing a 0.5 kg batch size, these ingredients were highintensity blended in a 4 liter HENSCHEL™ mixer for 1 minute.

The diluted formulations were then compounded on a DELTAPLAST™ extruder(typical output of approximately 6 kg/hr) having a 25 mm single screwwith an L/D ratio of 30:1 and equipped with a MADDOCKS™ mixer. Thebarrel temperature profile was set with a maximum zone setting ofapproximately 230° C. The molten polymer was filtered through a 60 meshscreen pack and then extruded through a strand die. The strand wassubsequently quenched in a water bath, dried, and pelletized.

The extruded pellets were molded into discs having a thickness of 1.27mm with a Carver Press exerting a hydraulic pressure of 13,000 psi and atemperature of 230° C. Specimens were taken from these discs fordifferential scanning calorimetry to determine the peak crystallizationtemperature (T_(c)).

TABLE 7 Nucleating agent loading, acid scavenger loading, and peak T_(c)of Examples 89-104. Nucleator Peak T_(c) Loading Acid NeutralizerLoading (° C.) Example 89 HPN-68L Calcium Propionate (C₃) 115.7 0.5 ppm500 ppm Example 90 HPN-68L Calcium Octanoate (C₈) 114.8 0.5 ppm 500 ppmExample 91 HPN-68L Calcium Caprate (C₁₀) 115.0 0.5 ppm 500 ppm Example92 HPN-68L Calcium Myristate (C₁₄) 117.3   1 ppm 500 ppm Example 93HPN-68L Calcium Pentadecanoate (C₁₅) 115.3 0.5 ppm 500 ppm Example 94HPN-68L Calcium Heptadecanoate (C₁₇) 116.2 0.5 ppm 500 ppm Example 95HPN-68L Calcium Stearate (C₁₈) 116.5 0.5 ppm 500 ppm Example 96 HPN-68LCalcium Stearate (C₁₈) 117.2   1 ppm 500 ppm Example 97 HPN-68L CalciumNonadecanoate (C₁₉) 116.5 0.5 ppm 500 ppm Example 98 HPN-68L CalciumBehenate (C₂₂) 118.2   1 ppm 500 ppm Example 99 HPN-68L PotassiumPropionate (C₃) 112.7 0.5 ppm 500 ppm Example 100 HPN-68L PotassiumOctanoate (C₈) 109.8 0.5 ppm 500 ppm Example 101 HPN-68L PotassiumCaprate (C₁₀) 110.7 0.5 ppm 500 ppm Example 102 HPN-68L PotassiumMyristate (C₁₄) 109.0   1 ppm 500 ppm Example 103 HPN-68L PotassiumStearate (C₁₈) 110.2 0.5 ppm 500 ppm Example 104 HPN-68L PotassiumStearate (C₁₈) 109.5   1 ppm 500 ppm

The composite peak crystallization value for the calcium salts (Examples89-98) was 116.3° C.+/−1.1° C. while the composite peak crystallizationvalue for the potassium salts (Examples 99-104) was 110.3° C.+/−1.3° C.

These data indicate that the carbon chain length does not have a verysignificant effect with respect to the acid neutralizer's ability tosubdue residual nucleation. On the other hand the metal associated withfatty acid salt appears to be the most significant factor with regard tothe acid neutralizer's ability to provide the desired lowcrystallization temperature of the polypropylene composition.

Example Set 9

All of the previous studies illustrated how certain acid neutralizerscan provide desired low or baseline crystallization temperatures inpolypropylene systems containing residual amounts of nucleator of 1 ppmand less. This experiment evaluates how potassium stearate affectsnucleation in PP systems having nucleator concentrations of 10 ppm allthe way up to conventional usage loadings of 500 ppm and 1000 ppm.Comparisons were also made to similarly nucleated systems containingcalcium stearate rather than potassium stearate.

To create the polypropylene compositions containing various levels ofHPN-68L nucleating agent, a concentrated nucleating agent mixture wasfirst formed by adding the following ingredients to PRO-FAX™ 6301 12 MFRPP homopolymer reactor flake: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and HPN-68L nucleator in anamount of 1000 ppm. Utilizing a 0.5 kg batch size, these ingredientswere high intensity blended in a 4 liter HENSCHEL™ mixer for 1 minuteforming the concentrated HPN-68L nucleating agent mixture.

Next, to PRO-FAX™ 6301 12 MFR PP homopolymer reactor flake, thefollowing ingredients were added: IRGANOX™ 1010 in an amount of 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and the concentrated nucleatingagent mixture in amounts ranging from 0.1% to 100%. In addition, theacid scavenger to be screened was also added at a concentrationconsistent with its use in commercial formulations. This serial dilutionresulted in final concentrations ranging from 1 to 1000 ppm of HPN-68Lnucleating agent in the formulation. Utilizing a 0.5 kg batch size,these ingredients were high intensity blended in a 4 liter HENSCHEL™mixer for 1 minute.

The diluted formulations were then compounded on a DELTAPLAST™ extruder(typical output of approximately 6 kg/hr) having a 25 mm single screwwith an L/D ratio of 30:1 and equipped with a MADDOCKS™ mixer. Thebarrel temperature profile was set with a maximum zone setting ofapproximately 230° C. The molten polymer was filtered through a 60 meshscreen pack and then extruded through a strand die. The strand wassubsequently quenched in a water bath, dried, and pelletized.

The extruded pellets were molded into discs having a thickness of 1.27mm with a Carver Press exerting a hydraulic pressure of 13,000 psi and atemperature of 230° C. Specimens were taken from these discs fordifferential scanning calorimetry to determine the peak crystallizationtemperature (T_(c)).

TABLE 8 Nucleating agent loading, acid scavenger loading, and peak T_(c)of Examples 105-115 Nucleator Peak T_(c) Loading Acid NeutralizerLoading (° C.) Example 105 HPN-68L Potassium Stearate 109.5   1 ppm 500ppm Example 106 HPN-68L Potassium Stearate 115.3  10 ppm 500 ppm Example107 HPN-68L Potassium Stearate 118.3  50 ppm 500 ppm Example 108 HPN-68LPotassium Stearate 120.3  100 ppm 500 ppm Example 109 HPN-68L PotassiumStearate 122.5  250 ppm 500 ppm Example 110 HPN-68L Potassium Stearate124.8  500 ppm 500 ppm Example 111 HPN-68L Calcium Stearate 117.2   1ppm 500 ppm Example 112 HPN-68L Calcium Stearate 120.7  10 ppm 500 ppmExample 113 HPN-68L Calcium Stearate 125.0  250 ppm 400 ppm Example 114HPN-68L Calcium Stearate 127.3  500 ppm 400 ppm Example 115 HPN-68LCalcium Stearate 129.0 1000 ppm 500 ppm

The preceding table illustrates again the effect of potassium stearateand calcium stearate on the polymer T_(c) at various nucleator loadings.

At low nucleator levels, potassium stearate provides T_(c) values nearthose from baseline polymer. As the amount of nucleator is increased, itbegins to outcompete this suppressive effect and can effectively performas a nucleating agent. While the T_(c) is never as high as with calciumstearate, this may provide a useful process in manufacturing to simplifymaterial supply or cleanout.

Example Set 10

Previous studies evaluated fatty acid salts at a typical commercialloading of around 500 ppm to understand their interaction with residualamounts of nucleator. This experiment seeks to determine if the desiredlow crystallization temperature can be enhanced by using higher loadingsof the acid scavenger.

To create polypropylene compositions having low levels of nucleatingagents, a concentrated nucleating agent mixture was first formed byadding the following ingredients to PRO-FAX™ 6301 12 MFR PP homopolymerreactor flake: IRGANOX™ 1010 in an amount of approximately 500 ppm,IRGAFOS™ 168 in an amount of 1000 ppm, and nucleator (either HPN-68L orHPN-20E) in an amount of 1000 ppm. Utilizing a 1 kg batch size, theseingredients were high intensity blended in a 10 liter HENSCHEL™ mixerfor 1 minute forming the concentrated nucleating agent mixture.

Next, to PRO-FAX™ 6301 12 MFR PP homopolymer reactor flake the followingingredients were added: IRGANOX™ 1010 in an amount of 500 ppm, IRGAFOS™168 in an amount of 1000 ppm, and the concentrated nucleating agentmixture in an amount of 1000 ppm. This serial dilution resulted in 1 ppmnucleating agent in the formulation. In addition, the acid scavenger tobe screened was also added at a concentration consistent with its use incommercial formulations and then also at a significantly higher loading.Utilizing a 0.5 kg batch size, these ingredients were high intensityblended in a 4 liter HENSCHEL™ mixer for 1 minute.

The diluted formulations were then compounded on a DELTAPLAST™ extruder(typical output of approximately 6 kg/hr) having a 25 mm single screwwith an L/D ratio of 30:1 and equipped with a MADDOCKS™ mixer. Thebarrel temperature profile was set with a maximum zone setting ofapproximately 230° C. The molten polymer was filtered through a 60 meshscreen pack and then extruded through a strand die. The strand wassubsequently quenched in a water bath, dried, and pelletized.

The extruded pellets were molded into discs having a thickness of 1.27mm with a Carver Press exerting a hydraulic pressure of 13,000 psi and atemperature of 230° C. Specimens were taken from these discs fordifferential scanning calorimetry to determine the peak crystallizationtemperature (T_(c)).

TABLE 9 Nucleating agent loading, acid scavenger loading, and peak T_(c)of Examples 116-135. Nucleator Peak T_(c) Loading Acid NeutralizerLoading (° C.) Example 116 HPN-20E Potassium Stearate 107.6 1 ppm  500ppm Example 117 HPN-20E Potassium Stearate 108.0 1 ppm 2000 ppm Example118 HPN-20E Sodium Stearate 111.0 1 ppm  500 ppm Example 119 HPN-20ESodium Stearate 111.5 1 ppm 2000 ppm Example 120 HPN-20E AluminumStearate 115.3 1 ppm  500 ppm Example 121 HPN-20E Aluminum Stearate114.2 1 ppm 2000 ppm Example 122 HPN-20E Magnesium Stearate 115.3 1 ppm 500 ppm Example 123 HPN-20E Magnesium Stearate 113.0 1 ppm 2000 ppmExample 124 HPN-20E Ca Stearoyl Lactylate 116.3 1 ppm (Pationic 930) 500ppm Example 125 HPN-20E Ca Stearoyl Lactylate 115.3 1 ppm (Pationic 930)1000 ppm Example 126 HPN-68L Potassium Stearate 109.5 1 ppm  500 ppmExample 127 HPN-68L Potassium Stearate 111.5 1 ppm 2000 ppm Example 128HPN-68L Sodium Stearate 117.6 1 ppm  500 ppm Example 129 HPN-68L SodiumStearate 118.7 1 ppm 2000 ppm Example 130 HPN-68L Aluminum Stearate109.0 1 ppm  500 ppm Example 131 HPN-68L Aluminum Stearate 109.8 1 ppm2000 ppm Example 132 HPN-68L Magnesium Stearate 111.5 1 ppm  500 ppmExample 133 HPN-68L Magnesium Stearate 107.2 1 ppm 2000 ppm Example 134HPN-68L Ca Stearoyl Lactylate 109.2 1 ppm (Pationic 930) 500 ppm Example135 HPN-68L Ca Stearoyl Lactylate 111.8 1 ppm (Pationic 930) 1000 ppm

Moving to higher loadings of acid scavenger did not appear tosignificantly affect the interaction of the fatty acid salt with theresidual amount of either HPN-68L or HPN-20E nucleator except formagnesium stearate. In this case (examples 122, 123, 132, and 133),moving from 500 ppm to 2000 ppm lowered the T_(c) by 2.3° C. and 4.3° C.in the presence of 1 ppm HPN-20E and 1 ppm HPN-68L respectively.

Apart from magnesium stearate, there was no consistent upward ordownward trend identified with how higher loadings of the other fattyacid salts affected the crystallization temperature of the polypropylenecomposition.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the subject matter of this application (especiallyin the context of the following claims) are to be construed to coverboth the singular and the plural, unless otherwise indicated herein orclearly contradicted by context. The terms “comprising,” “having,”“including,” and “containing” are to be construed as open-ended terms(i.e., meaning “including, but not limited to,”) unless otherwise noted.Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate the subject matter of theapplication and does not pose a limitation on the scope of the subjectmatter unless otherwise claimed. No language in the specification shouldbe construed as indicating any non-claimed element as essential to thepractice of the subject matter described herein.

Preferred embodiments of the subject matter of this application aredescribed herein, including the best mode known to the inventors forcarrying out the claimed subject matter. Variations of those preferredembodiments may become apparent to those of ordinary skill in the artupon reading the foregoing description. The inventors expect skilledartisans to employ such variations as appropriate, and the inventorsintend for the subject matter described herein to be practiced otherwisethan as specifically described herein. Accordingly, this disclosureincludes all modifications and equivalents of the subject matter recitedin the claims appended hereto as permitted by applicable law. Moreover,any combination of the above-described elements in all possiblevariations thereof is encompassed by the present disclosure unlessotherwise indicated herein or otherwise clearly contradicted by context.

What is claimed is:
 1. A process for extruding polypropylene comprising,in order: a. extruding a first composition through a first extruderforming a first extrudate and pelletizing the first extrudedcomposition, wherein the first composition comprises first reactor flakepolypropylene, a nucleating agent, and a first acid scavenger, whereinthe nucleating agent is in an amount of at least about 50 ppm; b.extruding a second composition through the first extruder immediatelyfollowing step a. forming a second extrudate and pelletizing the secondextruded composition, wherein the second composition comprises secondreactor flake polypropylene and a second acid scavenger, wherein thesecond acid scavenger is a potassium salt of a fatty acid, wherein thesecond extrudate contains between about 0.01 ppm and 1 ppm of thenucleating agent, and wherein the content of all nucleating agents inthe second extrudate is less than 10 ppm.
 2. The process of claim 1,wherein the first acid scavenger is selected from the group consistingof calcium stearate and hydrotalcite.
 3. The process of claim 1, whereinthe first acid scavenger and the second acid scavenger are the samecomposition.
 4. The process of claim 1, wherein the nucleating agentcomprises a cycloaliphatic metal salt.
 5. The process of claim 1,wherein the nucleating agent comprises at least one metal saltconforming to the structure of Formula (I)

where M₁ is an organic or inorganic cation, x is an integer from 1 to 2,and y is 1 or 2, wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, and R₁₀ areindividually selected from the group consisting of hydrogen, C₁-C₉alkyl, hydroxy, C₁-C₉ alkoxy, C₁-C₉ alkyleneoxy, amine, C₁-C₉alkylamine, halogen, and phenyl, wherein if such groups are alkyl, anytwo vicinal or geminal alkyl groups may be combined to form acarbocyclic ring of up to six carbon atoms, and wherein the carboxylmoieties of Formula (I) are present in cis configuration.
 6. The processof claim 5, wherein R₁-R₁₀ are hydrogen and M₁ is a calcium cation. 7.The process of claim 1, wherein the nucleating agent comprises abicyclic compound conforming with the structure of Formula (II)

wherein M₁₁ and M₁₂ are the same or different, or M₁₁ and M₁₂ arecombined to form a single moiety, and are independently selected fromthe group consisting of metal or organic cations, wherein R₂₀, R₂₁, R₂₂,R₂₃, R₂₄, R₂₅, R₂₆, R₂₇, R₂₈, and R₂₉ are independently selected fromthe group consisting of: hydrogen and C₁-C₉ alkyls, and further whereinany two adjacently positioned R₂₂-R₂₉ alkyl groups optionally may becombined to form a carbocyclic ring.
 8. The process of claim 7, whereinR₂₀-R₂₉ are hydrogen and M₁₁ and M₁₂ are sodium cations.
 9. The processof claim 1, wherein the first composition comprises the nucleating agentin an amount of at least about 100 ppm.
 10. The process of claim 1,wherein the second acid scavenger comprises a potassium cation and aC₃-C₂₂ fatty acid anion.
 11. The process of claim 1, wherein the secondacid scavenger comprises potassium stearate.
 12. The process of claim 1,wherein the difference between the T_(c) of the first extrudate and thesecond extrudate is greater than approximately 5° C.